Production of vitamin B12 in genetically engineered Propionibacterium freudenreichii

Abstract Since the chemical synthesis of vitamin B 12 requires more than 70 steps, the production of vitamin B 12 has been achieved by microorganism fermentation with additional brief chemical modifications. In an effort to increase the productivity of vitamin B 12 , we tried to express 10 genes belonging to the hem , cob and cbi gene families involved in the synthesis of vitamin B 12 in Propionibacterium freudenreichii , which is a known producer of vitamin B 12 . In a recombinant P. freudenreichii clone that harbored the expression vector containing a cobA , cbiLF , or cbiEGH , we obtained an increase in vitamin B 12 production of 1.7-, 1.9-, and 1.5-fold higher, respectively, than that in the microorganism without any cloned genes in the expression vector pPK705. The cobU and cobS genes caused a slight increase in the production of vitamin B 12 . Furthermore, we achieved multigene expression in P. freudenreichii . In a recombinant P. freudenreichii clone that harbored an exogenous gene, hemA , from Rhodobacter sphaeroides and endogenous hemB and cobA genes, we successfully achieved the production of about 1.7 mg/ l vitamin B 12 , 2.2-fold higher than that produced by P. freudenreichii harboring pPK705.